Burrow ventilation in the tube-dwelling shimp Callianassa subterranea (Decapoda: thalassinidea). III. Hydrodynamic modelling and the energetics of pleopod pumping.

1998 ◽  
Vol 201 (14) ◽  
pp. 2171-2181
Author(s):  
E J Stamhuis ◽  
J J Videler
Keyword(s):  
Phase Shift ◽  
Flow Velocity ◽  
Mechanical Efficiency ◽  
Added Mass ◽  
Force Balance ◽  
Power Stroke ◽  
Flat Plates ◽  
Recovery Stroke ◽  
The Mean ◽  
Callianassa Subterranea

The process of flow generation with metachronally beating pleopods in a tubiform burrow was studied by designing a hydrodynamic model based on a thrust-drag force balance. The drag of the tube (including the shrimp) comprises components for accelerating the water into the tube entrance, for adjusting a parabolic velocity profile, for accelerating the flow into a constriction due to the shrimp's body and another constriction due to the extended tail-fan, for shear due to separation and for the viscous resistance of all tube parts. The thrust produced by the beating pleopods comprises components for the drag-based thrust and for the added-mass-based thrust. The beating pleopods are approximated by oscillating flat plates with a different area and camber during the power stroke and the recovery stroke and with a phase shift between adjacent pleopod pairs. The added mass is shed during the second half of the power stroke and is minimized during the recovery stroke. A force balance between the pleopod thrust and the tube drag is effected by calculating the mean thrust during one beat cycle at a certain flow velocity in the tube and comparing it with the drag of the tube at that flow velocity. The energetics of the tube and the pump are derived from the forces, and the mechanical efficiency of the system is the ratio of these two. Adjusted to standard Callianassa subterranea values, the model predicts a mean flow velocity in the tube of 1.8 mm s-1. The mean thrust force, equalling the drag, is 36. 8 microN, the work done by the pleopod pump per beat cycle is 0.91 microJ and the energy dissipated by the tube system is 0.066 microJ per cycle. The mechanical efficiency is therefore 7.3 %. Pump characteristics that may be varied by the shrimp are the beat frequency, the phase shift, the amplitude and the difference in pleopod area between the power and recovery strokes. These parameters are varied in the model to evaluate their effects. Furthermore, the moment of added mass shedding, the distance between adjacent pleopods, the number of pleopods and the total tube drag were also varied to evaluate their effects.

Hydrodynamics of swimming in the water boatman, Cenocorixa bifida

1986 ◽  
Vol 64 (8) ◽  
pp. 1606-1613 ◽  
Author(s):  
R. W. Blake
Keyword(s):  
High Speed ◽  
Forward Direction ◽  
Added Mass ◽  
Mean Value ◽  
The Body ◽  
Power Stroke ◽  
Mass Force ◽  
Mean Power ◽  
Recovery Stroke ◽  
The Mean

Locomotion of a small water boatman (Cenocorixa bifida, Corixidae) was investigated employing high-speed cinematography and hydromechanical modelling based on a blade-element approach. The animal is propelled by the synchronous rowing action of its hind legs. The propulsive cycle consists of a power stroke and a recovery stroke phase. Force, impulse, power, and hydromechanical efficiency were calculated for a representative power stroke during which the mean body velocity was about 8 cms−1. A distinction is made between quasi-steady resistive and unsteady inertial (added mass) forces. The mean and maximum resistive thrust forces were calculated to be about 2.4 × 10−5 and 5.7 × 10−5 N per limb, respectively. By equating the total impulse of the power stroke for both legs (2.4 × 10−6 N s) with that of the drag force acting on the body over the same period, a drag coefficient of approximately 1.07 is inferred for the body. This value is comparable to those obtained for certain insects that operate at similar Reynolds numbers to C. bifida. The unsteady added mass force that acts in the forward direction is positive (propulsive) over most of the stroke with a mean value of about 1.17 × 10−5 N per limb, corresponding to an impulse of approximately 5.9 × 10−7Ns. The total propulsive mean force and impulse acting in the forward direction amount to about 3.6 × 10−5N and 1.8 × 10−6N s per limb, respectively, so the impulse of the forwardly directed added mass force amounts to about half that of the resistive thrust force. The total work and mean power associated with generating the resistive thrust were calculated to be about 6.7 × 10−7 J and 1.33 × 10−5 W per limb, respectively. Dividing the mean body drag power (1.4 × 10−5 W) by the total mean resistive power from both legs gave a hydromechanical efficiency of 0.52. When the mean inertial power associated with moving the body (2.3 × 10−6 W) and the added mass power required to accelerate and decelerate the legs (1.95 × 10−5 W per limb) are taken into account, the power stroke propulsive efficiency falls to 0.42. Taking the energy required to power the recovery stroke into account gives an overall propulsive cycle efficiency of about 0.40. This value is about twice that calculated in a previous study for drag-based pectoral fin rowing in the angelfish and reasons for this are suggested.

scholarly journals Burrow ventilation in the tube-dwelling shrimp callianassa subterranea (Decapoda: thalassinidea). II. The flow in the vicinity of the shrimp and the energetic advantages of a laminar non-pulsating ventilation current.

1998 ◽  
Vol 201 (14) ◽  
pp. 2159-2170 ◽  
Author(s):  
E J Stamhuis ◽  
J J Videler
Keyword(s):  
Flow Velocity ◽  
Power Stroke ◽  
Steady Flows ◽  
Mean Flow ◽  
Cross Sectional ◽  
Image Velocimetry ◽  
Cross Sectional Profile ◽  
Recovery Stroke ◽  
Sectional Profile ◽  
Callianassa Subterranea

The ventilation flow in the vicinity of the pleopod-pumping thalassinid shrimp Callianassa subterranea in an artificial transparent burrow has been mapped using particle image velocimetry. The flow in the tube in front of the shrimp was unidirectional, laminar and steady, with a parabolic cross-sectional velocity profile. The mean flow velocity was 2.0+/-0.1 mm s-1. The flow passed the thorax of the shrimp along the lateral and ventral sides. Ventral to the abdomen, the flow was dominated by the metachronally oscillating pleopods. The water around a pleopod is accelerated caudally and ventrally during the power stroke, and decelerated to a much lesser extent during the recovery stroke owing to a reduction in pleopod area. On average, the flow ventral to the abdomen converged towards the small opening underneath the telson, simultaneously increasing in velocity. A jet with a core velocity of 18-20 mm s-1 entered the area behind the shrimp from underneath the telson. This caused a separation zone with backflow caudal to the telson. Owing to the high rates of shear, the jet diverged and re-adjusted to a parabolic cross-sectional profile within 1-2 body lengths behind the shrimp, showing no traces of pulsation. The metachronal pleopod movements in combination with the increase in flow velocity at the constriction in the tube caused by the uropods and the telson probably prevented pulsation. The energetic consequences of pulsating and steady flows in combination with several tube configurations were evaluated. The results suggested that, by constricting the tube and keeping the flow steady, C. subterranea saves on ventilation costs by a factor of up to six compared with oscillatory flow in a tube without the tail-fan constriction.

A model for the micro-structure in ciliated organisms

1972 ◽  
Vol 55 (1) ◽  
pp. 1-23 ◽  
Author(s):  
John Blake
Keyword(s):  
Velocity Field ◽  
Plane Surface ◽  
Bending Moment ◽  
Power Stroke ◽  
Micro Structure ◽  
Mean Velocity ◽  
Slender Bodies ◽  
Recovery Stroke ◽  
The Mean ◽  
Bending Wave

Improved models for the movement of fluid by cilia are presented. A theory which models the cilia of an organism by an array of flexible long slender bodies distributed over and attached at one end to a plane surface is developed. The slender bodies are constrained to move in similar patterns to the cilia of the microorganismsOpalina, ParameciumandPleurobrachia.The velocity field is represented by a distribution of force singularities (Stokes flow) along the centre-line of each slender body. Contributions to the velocity field from all the cilia distributed over the plane are summed, to give a streaming effect which in turn implies propulsion of the organism. From this we have been able to model the mean velocity field through the cilia sublayer for the three organisms. We find that, in a frame of reference situated in the organism, the velocity near the surface of the organism is very small – up to one half the length of the cilium – but it increases rapidly to near the velocity of propulsion from then on. This is because of the beating pattern of the cilia; they beat in a near rigid-body rotation during the effective (‘power’) stroke, but during the recovery stroke move close to the wall. Backflow (‘reflux’) is found to occur in the organisms exhibiting antiplectic metachronism (i.e.ParameciumandPleurobrachia). The occurrence of gradient reversal, but not backflow, has recently been confirmed experimentally (Sleigh & Aiello 1971).Other important physical values that are obtained from this analysis are the force, bending moment about the base of a cilium and the rate of working. It is found, for antiplectic metachronism, that the force exerted by a cilium in the direction of propulsion is large and positive during the effective stroke whereas it is small and negative during the recovery stroke. However, the duration of the recovery stroke is longer than the effective stroke so the force exerted over one cycle of a ciliary beat is very small. The bending moment follows a similar pattern to the component of force in the direction of propulsion, being larger in the effective stroke for antiplectic metachronism. In symplectic metachronism (i.e.Opalina) the force and bending moment are largest in magnitude when the bending wave is propagated along the cilium. The rate of working indicates that more energy is consumed in the effective stroke forParameciumandPleurobrachiathan in the recovery stroke, whereas inOpalinait is found to be large during the propagation of the bending wave.

scholarly journals Biomechanics of Frog Swimming: I. Estimation of the Propulsive Force Generated by Hymenochirus Boettgeri

1988 ◽  
Vol 138 (1) ◽  
pp. 399-411 ◽  
Author(s):  
JULIANNA M. GAL ◽  
R. W. BLAKE
Keyword(s):  
Recovery Phase ◽  
Added Mass ◽  
The Body ◽  
Force Balance ◽  
Upper And Lower Bounds ◽  
Power Stroke ◽  
Propulsive Force ◽  
Body Velocity ◽  
Hymenochirus Boettgeri ◽  
Single Sequence

Ciné films were used to study swimming in the frog, Hymenochirus boettgeri (Tornier) during near-vertical breathing excursions. The animals generally decelerated during hindlimb flexion (recovery phase) and accelerated throughout hindlimb extension (power phase). Body velocity patterns of frogs are distinct from those of other drag-based paddlers, such as angelfish and water boatman, where the body is accelerated and decelerated within the power stroke phase. The propulsive force, estimated for a single sequence from quasi-steady drag and inertial considerations, was positive throughout extension. The upper and lower bounds of this estimate were calculated by considering additional components of the force balance, including the net effect of gravity and buoyancy, and the longitudinal added mass forces associated with the body. Consideration of the force balance implies that simple drag-based propulsion may not be sufficient to explain the swimming patterns observed in frogs.

Design and Dynamic Modeling of a Flexible Feathering Joint for Robotic Fish Pectoral Fins

2014 ◽  
Author(s):  
Sanaz Bazaz Behbahani ◽  
Xiaobo Tan
Keyword(s):  
Dynamic Model ◽  
Robotic Fish ◽  
Power Stroke ◽  
Hydrodynamic Drag ◽  
Pectoral Fin ◽  
Flexible Joint ◽  
Blade Element Theory ◽  
Pectoral Fins ◽  
Flexible Part ◽  
Recovery Stroke

In this paper, we propose a novel design for a pectoral fin joint of a robotic fish. This joint uses a flexible part to enable the rowing pectoral fin to feather passively and thus reduce the hydrodynamic drag in the recovery stroke. On the other hand, a mechanical stopper allows the fin to maintain its motion prescribed by the servomotor in the power stroke. The design results in net thrust even when the fin is actuated symmetrically for the power and recovery strokes. A dynamic model for this joint and for a pectoral fin-actuated robotic fish involving such joints is presented. The pectoral fin is modeled as a rigid plate connected to the servo arm through a pair of torsional spring and damper that describes the flexible joint. The hydrodynamic force on the fin is evaluated with blade element theory, where all three components of the force are considered due to the feathering degree of freedom of the fin. Experimental results on robotic fish prototype are provided to support the effectiveness of the design and the presented dynamic model. We utilize three different joints (with different sizes and different flexible materials), produced with a multi-material 3D printer, and measure the feathering angles of the joints and the forward swimming velocities of the robotic fish. Good match between the model predictions and experimental data is achieved, and the advantage of the proposed flexible joint over a rigid joint, where the power and recovery strokes have to be actuated at different speeds to produce thrust, is demonstrated.

Experimental Study on Hydraulic Roughness of Submerged Grass in Ecological Riverbank

2013 ◽  
Vol 838-841 ◽  
pp. 1743-1748
Author(s):  
Dian Guang Ma ◽  
Chun Xin Zhong ◽  
Wu Ning ◽  
Qing Ye ◽  
Sheng Zhu
Keyword(s):  
Flow Velocity ◽  
Roughness Coefficient ◽  
Theoretic Analysis ◽  
Mean Flow ◽  
Normal Range ◽  
Obvious Effect ◽  
Hydraulic Roughness ◽  
Natural Turf ◽  
Scouring Process ◽  
The Mean

A model experiment about the hydraulic roughness of natural turf used in riverbank was carried out in flume. To examine the rationality of experimental design, the hydraulic roughness coefficient of plexiglass-flume was tested firstly. The result was 0.0085, which is quite normal. Then the tested hydraulic roughness caused by vegetation ranges from 0.020 to 0.090 for the chosen plants, which is also acceptable. Furthermore, the tested incipient velocities of krasnozem, and paddysoil had the range of 0.55~0.65m·s-1 and 1.0~1.1m·s-1, respectively. All these experimental results are in normal range, which means that the design of this experimental is rational. Experimental research illustrate that, the roughness coefficient of plant reduces with the increasing of flow velocity. When the mean flow velocity is over 3m·s-1, Mannings n values vary between 0.025 and 0.035. This phenomenon is accord with the theoretic analysis. During the scouring process, not only the flow velocity, but also the flow duration has an obvious effect on the coarseness of vegetative bed.

Experimental Investigation of the Acoustic Reflection Coefficient of a Modeled Gas Turbine Impingement Cooling Section

2012 ◽  
Author(s):  
Christoph Jörg ◽  
Michael Wagner ◽  
Thomas Sattelmayer
Keyword(s):  
Reflection Coefficient ◽  
Flow Velocity ◽  
Gas Turbines ◽  
Acoustic Energy ◽  
Quality Data ◽  
Mean Flow ◽  
Impingement Cooling ◽  
Acoustic Reflection ◽  
The Mean ◽  
Mean Flow Velocity

The thermoacoustic stability of gas turbines depends on a balance of acoustic energy inside the engine. While the flames produce acoustic energy, other areas like the impingement cooling system contribute to damping. In this paper, we investigate the damping potential of an annular impingement sleeve geometry embedded into a realistic environment. A cold flow test rig was designed to represent real engine conditions in terms of geometry, and flow situation. High quality data was delivered by six piezoelectric dynamic pressure sensors. Experiments were carried out for different mean flow velocities through the cooling holes. The acoustic reflection coefficient of the impingement sleeve was evaluated at a downstream reference location. Further parameters investigated were the number of cooling holes, and the geometry of the chamber surrounding the impingement sleeve. Experimental results show that the determining parameter for the reflection coefficient is the mean flow velocity through the impingement holes. An increase of the mean flow velocity leads to significantly increased damping, and to low values of the reflection coefficient.

scholarly journals Doppler ultrasound of umbilical artery in prediction of fetal outcome in pregnancy induced hypertension Sudanese population

2019 ◽  
Vol 8 (1) ◽  
pp. 96
Author(s):  
Rihab A. Yousif ◽  
Awadia G. Suliman ◽  
Raga A. Aburaida ◽  
Ibrahim M. Daoud ◽  
Naglaa E. Mohammed
Keyword(s):  
Flow Velocity ◽  
Umbilical Artery ◽  
Fetal Outcome ◽  
Fetal Mortality ◽  
Pregnancy Induced Hypertension ◽  
Diastolic Flow ◽  
Induced Hypertension ◽  
The Mean ◽  
Doppler Indices ◽  
In Pregnancy

The pregnancy induced hypertension increase the fetal mortality and morbidity and the using of Doppler umbilical artery indices decrease the fetal mortality and morbidity however, there is few complete data about the most frequently altered Doppler US parameters to predict fetal outcome in pregnancy induced hypertension . Methods This ia cohort prospective study done in two hundred and six women of second and third trimester presenting to antenatal clinic in Soba University Hospital at the department of Obstetrics & Gynecology, in the fetus unit and critical pregnancy in the period From June 2008 to April 2013 to assess the Doppler indices of umbilical artery in pregnancy induced hypertension for prediction of prenatal outcome; 105 pregnancy induced hypertension patients and 101 women with uneventful pregnancies as normal control group included in this study . Baseline investigations and color Doppler of umbilical artery were done. Statistical analysis of data were done using SPSS, Receiver Operating Characteristic (ROC) curve analysis was performed and the area under the curve (AUC) used to determine sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of umbilical artery Doppler indices to predict fetal outcome.Results The study determine that there was significant difference in Doppler indices in PIH and control group ( p<0.01, the mean indices of umbilical artery is higher in PIH group compared with normal pregnancy group , the mean different of S/D ratio was 0.40, mean difference of RI was 0.06 and the mean different of PI index was 0.16, high percentage of adverse fetal outcome had been reported in in Pregnancy Induced Hypertension group than in control , which was more in absent and reversed flow velocity in umbilical artery in Pregnancy Induced Hypertension compared with group of Pregnancy Induced Hypertension with present end diastolic flow velocity. Systolic/Diastolic ratio was most accurate in predicting adverse outcome in pregnancy induced hypertension patients, followed by the Pulastility index then the Resistance index (75%, 66% and 57% respectively).ConclusionThis study concluded that pregnancy induced hypertension leads to worsen placental insufficiently, which appears on the higher Doppler indices of umbilical artery to PIH patients when compared with normal pregnancy. A low diastolic flow and higher indices characterized the pregnancies with abnormal outcomes. Doppler of the umbilical artery was useful to predict fetal well being in PIH patients, high percentage of adverse fetal outcome had been reported in absent and reversed end diastolic flow velocity in umbilical artery compared with group of present flow velocity.

Added mass of thin flat plates of arbitrary shapes with possible openings

2018 ◽  
Vol 79 ◽  
pp. 149-159 ◽  
Author(s):  
Mohamed Hariri Nokob ◽  
Ronald W. Yeung
Keyword(s):  
Added Mass ◽  
Flat Plates ◽  
Arbitrary Shapes

The Swimming of Nymphon Gracile (Pyconogonida)

1971 ◽  
Vol 55 (1) ◽  
pp. 273-287
Author(s):  
ELFED MORGAN
Keyword(s):  
Angular Velocity ◽  
Hydrodynamic Force ◽  
Beat Frequency ◽  
High Elevation ◽  
Dorsal Side ◽  
Constant Angular Velocity ◽  
Power Stroke ◽  
Lateral Thrust ◽  
Constant Depth ◽  
Recovery Stroke

1. The organization of the swimming legs of N. gracile has been described. The legs beat ventrally so the animal swims with the dorsal side foremost. The joints between the major segments of the leg are extended for most of the power stroke, but the distal segments articulate sequentially later in the beat, commencing with the flexion of the femoro-tibial joint at the end of the power stroke. Continued flexion reduces the leg radius considerably during the recovery stroke. 2. Animals swimming at constant depth were found to have a leg-beat frequency of about 1 beat/s. Above this the rate of ascent increased rapidly with increasing frequency of beat. Abduction or adduction of the leg usually occurred prior to the start of the power stroke with the femur in the elevated position. 3. Assuming a fixed limb profile at constant angular velocity, maximum lift was calculated to have occurred with the femur inclined at an angle of about 50° to the dorso-ventral body axis. The outward component of the lateral thrust decreased to zero at this point, and with further declination of the femur the lateral forces became inwardly directed. Of the different segments of the leg, tibia 2 and the tarsus and propodium contribute most of the hydrodynamic force. 4. The angular velocity of the leg varied during the power stroke, and the actual forces generated during two beats having the same amplitude and angular velocity but of high and low elevation were calculated. Greater lift occurred during the high-elevation beat when the leg continued to provide lift throughout the power stroke, whereas the low-elevation beat acquired negative lift values towards the end of the power stroke. The lateral thrust was now directed entirely inwards.

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